sergiu

Will this thing cut off at 2.8V to protect the battery from over-discharge? Looking at the schematic it looks like it can go as low as 1.7V which will certainly damage the lipo and in some cases might even cause fire. It would be nice to have such a feature on board since you went to the trouble to add the charging chip, etc.

I use Tack Putty (http://www.google.com/products?q=elmer%27s+tack). Elmer’s brand is great. Just warm it up a little and use it to hold headers and parts while the board is upside down. It cleans up easily with a bigger piece.
My favorite tool for correcting soldering mistakes is Hakko de-soldering gun 808 - if you can afford it buy yourself a present this Christmas.

To [Almost_there] : temperature of the soldered device should not exceed 260C (500F), in most cases (but check the device datasheet, some datasheets even have reflow profile charts, and you should try to follow those). I like to use a thermal probe connected to a multimeter, right next to the device and monitor the actual temperature. I set the temperature on hot air station to about 300C-350C. You need to control the temperature by how far you keep the nozzle from the device. Start 5-6 inches away then slowly move towards the device, with spiral motion , if you see you’re exceeding 500F move back up or you could damage the device. If you don’t have hot air station a regular hot air gun will do (if it can reach 260C/500F).
Also, this walk-through might be of interest to anyone attempting to do leadless smd soldering for the first time:http://starlino.com/surface_mount_reflow.html

I got an update on the sensitivity issue. All this time I was doing testing on X axis, but now when I decided to thoroughly test the Y axis (why I didn’t do it earlier !) it turns out it outputs a constant 1.1V . It would however set to 1.35 with an autozero (AZ) pulse, but will still not react to any movement. So finally I came to the conclusion the particluar device I received was miss- calibrated from the factory. I’ll try contacting Sparfun to see if I can get this resolved.

Why were you testing the unit at 132 Deg/sec when its >range is +/- 67deg/sec?
The answer is because I can (as I explained the sensitivity is 5mV/sec/deg, instead of 15mV/sec/deg), as a result the range is increased. This chip is obviously miss-labeled, or calibrated wrongly at the factory, very weird …

It looks like the unit I received has a sensitivity of 5mV/Deg/Sec (instead of 15 mV/Deg/Sec as stated in datasheet) and consequently a range of 1.35/0.005 = 270 deg/sec.
First I noticed that my data readings are 3 times lower than it’s supposed to be (15/5= 3). (I was integrating the gyro readings and comparing with accelerometer data).
Then I decided to do a simple experiment, I mounted the gyro on a spinning wheel (drived by a servo) . I measured the rpm using a tachometer (and also by counting cycles). I got 22 rpm and the reading from X output of gyroscope was 0.66V , another test by spinning in oposite direction was ( 27.7rpm and 2.15 V).
Making simple calcualations I got:
22rpm = 22 * 360 Deg / 60 sec = 132 Deg / sec
Delta V = 2.7V/2 - 0.66V = 1.35V - 0.66V = 0.69V
From this sensitivity = 0.69V / 132 Deg /sec = 0.00523 V/Deg/sec
If you do calculations for the other measurment (27.7rmp 1.41 V you’ll get similar results 0.8/166.2 = 0.00481 V/Deg/sec).
Now am I missing something or is device out of spec ? Did anyone else got same issue ?

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